Thanks, Lyndal, for letting us know.
Winfrey, I am so sorry for your and Carol's loss. That is such a difficult thing to go through.
Unless you are planning on breeding Cody, I'd get him neutered as soon as possible. I have been where you are with feuding dogs and it is so very difficult.
I have seen several dog therapist talk about being sure that both dogs know who is in charge (you and Carol) and advise keeping both feuding dogs as tired out as possible. They usually accomplish this by frequent walks of an hour or so (often with backpacks) and with fun activities such as Agility Training, but not by playing or other activities which create excitement.
I know with my pack of 4, the older 3 often growl or snap at Skywalker but it is often (though not always) as a result of something Sky did first (a look etc). No matter, I am immediately in the middle of it letting them all know it is not OK no matter who started it. They are sometimes upstairs with me down when this starts, but they all recognize my "Stop it" yell (though yelling is not generally encouraged during this time), and by the time I actually get upstairs they are all sitting down looking quite innocent.
Also, sometimes one of the dogs will try to "own" one of the humans by warning the other dogs away. That is immediately and firmly rejected by us (I send the claiming dog away from me) as that can be a cause of fighting.
Some trainers also say that separating the dogs just makes 2 packs and encourages fights. Hubby and I are careful to switch out who is leading which dog when we are walking/hiking to be sure that all the dogs realize we are 1 pack and they don't get to control it. We also are careful to be even handed with who can sit on the sofa with us or be next to us in bed, etc. Can you muzzle them so they can be together, and then discipline the aggressor when necessary?
I know I often end up disciplining both dogs when I'm not sure which one started it.
None of this may apply to your situation, but it may.
Good luck and hugs to you all.
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"Dogs are not our whole life, but they make our lives whole."
-Roger Caras